1. Field of the Invention
This present invention relates generally to microwave devices, and more particularly, to antenna arrays.
2. Related Art
In today's modern society satellite communication systems have become common place. There are now numerous types of communication satellites in various orbits around the Earth transmitting and receiving huge amounts of information. Telecommunication satellites are utilized for microwave radio relay and mobile applications, such as, for example, communications to ships, vehicles, airplanes, personal mobile terminals, Internet data communication, television, and radio broadcasting. As a further example, with regard to Internet data communications, there is also a growing demand for in-flight Wi-Fi® Internet connectivity on transcontinental and domestic flights. Unfortunately, because of these applications, there is an ever increasing need for the utilization of more communication satellites and the increase of bandwidth capacity of each of these communication satellites.
An obvious problem to solving this need is that individual communication satellite systems are very expensive to fabricate, place in Earth orbit, and operate and maintain. Another problem to solving this need is that there are limiting design factors to increasing the bandwidth capacity in a new communication satellite. One of these limiting design factors is the relative compact physical size and weight of a communication satellite. Communication satellite designs are limited by the size and weight parameters that are capable of being loaded into and delivered into orbit by a modern satellite delivery system (i.e., the rocket system). The size and weight limitations of the communication satellite limit the type of electrical, electronic, power generation, and mechanical subsystems that may be included in the communication satellite. As a result, the limit of these types of subsystems are also limiting factors to increasing the bandwidth capacity of the satellite communication.
It is appreciated by those skilled in the art, that in general, the limiting factors to increased bandwidth capacity of the communication satellite are determined by the transponders, antenna system(s), and processing system(s) of the communication satellite.
With regard to the antenna system (or systems), most communication satellite antenna systems include some type of antenna array system. In the past reflector antennas (such as parabolic dishes) were utilized with varying numbers of feed array elements (such as feed horns). Unfortunately, typically these reflector antenna systems scanned their antenna beams utilizing mechanical means instead of electronic means. These mechanical means generally include relatively large, bulky, and heavy mechanisms (i.e., antenna gimbals).
More recently, there have been satellites that have been designed utilizing non-reflector phased array antenna systems. These phased array antenna systems are capable of increasing the bandwidth capacity of the antenna system as compared to previous reflector type of antenna systems. Additionally, these phased array antenna systems are capable of directing and steering antenna beams sometimes without mechanically moving the phase array antenna system. Generally, dynamic phased array antenna systems utilize variable phase shifters to move the antenna beam without physically moving the phased array antenna system. Fixed phased array antenna systems, on the other hand, utilize fixed phased shifters to produce an antenna beam that is stationary with respect to the face of the phased array antenna system. A such, fixed phased array antenna systems require the movement of the entire antenna system (with for example, an antenna gimbal) to directing and steering the antenna beam.
Unfortunately, while dynamic phased array antenna systems are more desirable then fixed phased array antenna systems they are also more complex and expensive since they require specialized active components (such as power amplifiers and active phase shifters) and control systems. As such, there is a need for a new type of phased array antenna system capable of electronically scanning an antenna beam that is robust, efficient, compact, and solves the previously described problems.